JP2669823B2 - Silicon film growth method - Google Patents

Description

The present invention relates to a method for epitaxially growing single crystal silicon on an insulating film or an insulating base in order to form an SOI structure. (B) Conventional technology An SOI (Silicon On In Insulator) is a device in which a single crystal silicon film is formed on an insulating film or an insulating base (hereinafter referred to as an insulating base).
SOS) structure, especially SOS with an insulation base of SOS
It is called a (Silicon On Sapphire) structure, and is known to be capable of achieving high integration and high speed in a semiconductor integrated circuit. When a silicon film is crystallized on an insulating base, the insulating base needs to be cleaned as a pretreatment, but it has been necessary to clean at a temperature as low as possible in order to avoid adverse effects such as auto doping. For example, in Japanese Patent Laid-Open No. 62-90921 (H01L21 / 20),
In a method of epitaxially growing silicon on a base made of a silicon wafer, a sapphire substrate, etc., a high-frequency electric field is applied to an inert gas for ionization,
It describes that a constant voltage is applied to the base, the base surface is sputter-cleaned with an ionized inert gas, and then silicon is epitaxially grown on the base surface. (C) Problems to be Solved by the Invention In the conventional example, both the cleaning of the base and the epitaxial growth of silicon are performed at a temperature of 800 ° C. In the temperature condition of 800 ° C. for both the cleaning and the growth, although the auto-doping to the growth layer is suppressed, the grown silicon film has many defects (the defect density is 6.9 × 10 ⁴ cm ^{−2 according} to the measurement by the present inventors). (Badly), there is a problem that the film quality for practical use cannot be obtained. This is also true under the temperature condition of 850 ° C. for both cleaning and growth. The present invention relates to a method for growing a silicon film and solves such a problem. (D) Means for Solving the Problems The present invention is a method for growing a single crystal of a silicon film on an insulating base, which comprises applying a high-frequency electric field to an inert gas for ionization and at the same time applying the base to the base. The surface of the base is sputter-cleaned with the ionized inert gas by applying a constant voltage, and a silicon film is epitaxially grown on the base at a temperature higher than that at the time of cleaning and less than 950 ° C. (E) Action In other words, by causing the silicon film to grow epitaxially at a base temperature higher than that during sputtering cleaning,
A single crystal silicon film with few defects can be obtained on the insulating base. Moreover, by setting the temperature at the time of epitaxial growth to less than 950 ° C., autodoping of the growth layer is also suppressed. (F) Example FIG. 1 shows a CVD apparatus according to the present invention, in which 1 is a reaction tube made of quartz or the like, a gas introduction tube 2 is provided at one end, and an exhaust tube 3 is provided at the other end. Reference numeral 4 denotes a susceptor in which carbon is coated with SiC, and is heated by an infrared lamp 5 outside the reaction tube 1. The temperature of the susceptor 4 is measured by a thermocouple 7 and a voltage is applied from a DC power supply 8. Reference numeral 9 denotes a coil provided on the upstream side of the position of the susceptor 4 of the reaction tube 1 so as to wind around the reaction tube 1. Reference numeral 10 denotes a high-frequency power supply connected to the coil 9; Generates a high frequency of 50W. A case where a silicon film is epitaxially grown using such an apparatus will be described with reference to FIG. As the insulating base, a sapphire base, a magnesia spinel single crystal substrate or a magnesia spinel single crystal film formed on the surface of the substrate is used. First, the insulating base 21 that has been chemically cleaned is placed on the susceptor 4, and the inside of the reaction tube 1 is evacuated from the exhaust pipe 3 to a level of 10 ⁻⁷ Torr by, for example, a turbo molecular pump to remove residual gas. Then, the infrared lamp 5 heats the base 21 to raise the temperature. The set temperature at this time is, for example, 800 ° C. as a temperature required for cleaning the surface of the base. The inside of the reaction tube 1 and the base 21 are baked by maintaining this set temperature for a certain time (for example, about 1 hour). And, in a state close to the vacuum degree before temperature rise,
Ar gas is supplied from the gas introduction pipe 2 at a flow rate of 30 cc / min (at this time, the partial pressure of Ar is about 150 mTorr). Ar plasma is generated in the reaction tube 1 by applying a high frequency to the coil 9. Then, a DC bias voltage (for example, 300
V) is applied and Ar plasma is collided with the surface of the base 21 to clean the surface of the base by sputtering. The degree of cleaning is controlled by the sputtering time, and when the base temperature is 800 ° C, it may be about 3 minutes. When the sputtering cleaning is completed (Fig. 2A),
The application of the DC bias voltage to the susceptor 4 is stopped, and SiH ₄ gas (SiH ₄ gas partial pressure is about 70 mTorr) is supplied together with Ar gas from the gas introduction pipe 2 at a flow rate of 10 cc / min. At the same time, the infrared lamp 5 is used to adjust the base temperature to the growth temperature of 850
Heat to ℃ and raise the temperature. After generating plasma with a mixed gas of Ar gas and SiH ₄ gas for several tens of seconds, the high frequency output was set to 20
Drop to W or reduce to zero, plasma CVD method or low pressure CVD
A silicon film is epitaxially grown by the method. Here, the base temperature is 5 to increase from 800 ℃ to 850 ℃.
It takes about a minute, so it has not reached 850 ℃ at this point. Therefore, the SiH ₄ gas partial pressure is lowered from about 70 mTorr to about 25 mTorr in order to suppress the growth of the silicon film to the growth temperature as much as possible. When the base temperature is 800 ° C, the SiH ₄ gas partial pressure is about 70 mTorr and the silicon film growth rate is about 700 Å / min.
Since the iH ₄ gas partial pressure is about 25 mTorr and the growth rate is about 100 ° / min, a silicon film 22 ′ of about 500 ° grows epitaxially until the base temperature reaches 850 ° C. (FIG. 2B). When the temperature of the base reaches 850 ° C., the partial pressure of the SiH ₄ gas is returned to about 70 mTorr, and the epitaxial growth is continued until a desired thickness (for example, 0.3 μm) is reached. However, the base temperature is kept at 850 ° C. Thus, a high-quality single crystal silicon film 22 having a low defect density (= 6.9 × 10 ³ cm ⁻² ) is obtained (FIG. 2C). As described above, the defect density of the silicon film obtained at the cleaning temperature of 800 ° C. and the growth temperature of 800 ° C. is about 6.9 × 10 ⁴ cm ⁻² , while in the present embodiment, the cleaning temperature of 800 ° C. Defect density of silicon film obtained at ℃ ℃, growth temperature 850 ℃ 6.9 × 10 ³ cm
^-2 , the defect density is remarkably reduced, and a high-quality silicon film with very few defects can be obtained. Here, when the silicon film is epitaxially grown at a cleaning temperature of 850 ° C. and a growth temperature of 850 ° C., the defect density is 2.2 × 1.
It will be very large, 0 ⁵ cm ^-2 . This is because the cleaning action by sputtering is promoted by the thermal effect,
It is considered that the surface of the base is rather roughened, and many crystal defects are introduced into the silicon film grown on the surface of the roughened base. Therefore, the base temperature in the sputtering cleaning has an upper limit of about 800 ° C. Also,
The base temperature for epitaxial growth is preferably set to a temperature lower than 950 ° C. in order to avoid autodoping (eg, A1) from the base to the silicon film. In this example, by setting the base temperature during epitaxial growth to around 850 ° C., which is lower than 950 ° C.,
It also suppresses auto-doping of impurities from the base. (G) Effect of the Invention In the method for growing a silicon film of the present invention, a single crystal having a low defect density is formed on the insulating base by causing the silicon film to grow epitaxially at a base temperature higher than that during sputtering cleaning. A silicon film can be obtained. Moreover, by setting the temperature during the epitaxial growth to less than 950 ° C., it is possible to suppress the autodoping of the growth layer. Therefore, a high quality device for practical use can be formed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of a CVD apparatus according to the method of the present invention, FIG.
The drawings are process explanatory views showing an embodiment of the present invention. 1 ... reaction tube, 2 ... gas introduction tube, 3 ... exhaust tube, 4 ...
… Susceptor, 5… infrared lamp, 7… thermocouple, 8…
… DC power supply, 9 …… coil, 10 …… high frequency power supply, 21 ……
Insulation base, 22 ... Silicon film.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Shiro Nakanishi               2-18 Keihanhondori, Moriguchi City SANYO Electric               Inside the corporation (72) Inventor Toru Dan               2-18 Keihanhondori, Moriguchi City SANYO Electric               Inside the corporation                (56) References Japanese Patent Publication Sho 47-12060 (JP, B1)

Claims (1)

(57) [Claims] A method for growing a single crystal of a silicon film on an insulating base, wherein a high frequency electric field is applied to an inert gas to ionize the same, and a constant voltage is applied to the insulating base to form a base with the ionized inert gas. Clean the surface of the table by sputtering, and place it on the base at a higher temperature and
A method for growing a silicon film, which comprises epitaxially growing the silicon film at a temperature lower than 0 ° C.